I have 33/6.6 KV 20 MVA trafo feeding 8 nos of 2 MVA trafos. One of the trafos is feeding AC drives; the total KW of the connected loads is about 1000 KW. The motor capacities range from 11 KW to 110 KW.

How to calculate / know whether harmonic filters will be required on the 6.6 KV bus or not ?

Thanks,
easyser

Dear easyser,
without any calculation, I could tell you that you will have benefits using low-voltage harmonic filters for such type of load.
Harmonic filtering on 6.6 kV bus is a costly solution, what kind of load do you have on other 7 trafos?

Surely an additional harmonic filter will improve general efficiency and reliability of inverters and other electrical devices connected.
What kind of plant do you face? It is interesting to know if 1000 kW is a stable load or there are many intermittent loads. What is the low voltage to inverter drives?


Regards
Mario

Dear Mtr Mario,

The other trafos have induction motor loads. The trafo ratings are 6. KV/ 415 V 2 MVA.

The 1000 KW inverter load is more or less a constant load. The input supply to the inverters is 415 Volts.

The plant is a process plant.

Dear easyser,
for your application I would suggest to install one or more non-tumed passive filter in series on power supply at 415 V, only to inverters.
Depending from spece/money availability, you can select one of these option:
A ) to install only one big filter in series with secondary trafo, 2000 A or something like this.
B ) to install more small filters, i.e. 4 units 500 A if the output current should be divided
C ) to install few small filters, for partial harmonic filtering.

In case of option C you will have in future the possibility to complete filtering using aditional filters.

I don't know in which country you have to install this plant, therefore I cannot give you more info regarding standards or local laws about harmonics. Generally speaking, I think that in your case harmonics filters are not mandatory, but they are useful for a better reliability and efficiency.

You can download a software (but you have to register, free) on Mirus site, for example.

Regards
Mario

Dear Mr Mario,

Thanks for the useful reply and also suggesting Mirus site. I found that site quite useful.

Regards,
easyser